1. Field of the Invention
This present invention relates to footwear. More particularly, the present invention relates to midsoles designed to meet the performance requirements of different wearers and applications.
2. Description of the Related Art
Different activities, such as, for example, running, walking, basketball, and tennis, have different performance requirements. For example, runners are exposed to repeated pounding in their feet, legs, and back, as their feet come into contact with the ground. The repeated pounding results in the transmission of ground reaction forces to the feet and other parts of the anatomy, such as, for example, the knees, the hips, etc. Ground reaction forces are generally transmitted from the ground surface to the foot upon impact of the foot with the ground. Repeated exposure to ground reaction forces takes its toll on the human body, often times resulting in chronic injuries. In some instances, the injury is much more acute and occurs only after a short period of exposure to ground reaction forces.
Certain types of activities have particular performance requirements. For example, individuals engaged in cutting motions generally need more vertical stability (i.e. less compressibility) in the lateral forefoot region. Similarly, individuals engaged in activities that involve running need more vertical stability in the toe region to facilitate the toe-off phase of a typical gait. Consequently, it is desirable to design a shoe that reduces the effect of ground reaction forces transmitted to the wearer during the activities associated with an application without compromising the performance needs associated with the activities.
Manufacturers have experimented with various materials and designs with the goal of providing shock attenuation and energy absorption in the midsole of the shoe. The xe2x80x9cone size fits allxe2x80x9d approach used by a variety of prior shoe designs is often an inaccurate approach to addressing the shock attenuation needs of the wearer because people with the same shoe size may have markedly different physical characteristics, such as weight and distribution of weight. People with different physical characteristics frequently have different shock attenuation needs.
Therefore, there remains a need for midsole designs that allow the midsoles to selectively attenuate ground reaction forces by taking into consideration the physical characteristics of the people wearing the shoes and the performance requirements of the applications for which the shoes are worn. Notwithstanding the variety of prior shoe designs, there remains a need for shoe midsoles that provide the appropriate amount of shock attenuation in the appropriate areas of the feet to individuals engaged in particular types of activities.
The present invention provides for a shoe midsole with zones designed to meet the performance requirements of a given activity. The present invention also comprises a method for designing a shoe midsole to meet the performance requirements of a specific application.
In one embodiment, the shoe midsole comprises a support structure, a plurality of cells, and a plurality of midsole zones that are designed to provide specific targeted vertical deceleration levels.
In one embodiment, at least one of the midsole zones comprises a performance zone and at least one of the midsole zones comprises a comfort zone, wherein each performance zone has a targeted vertical deceleration level higher than that for each comfort zone, and wherein at least some of the cells within each performance zone have angles of drafting less than at least some of those in each comfort zone.
In one embodiment, the midsole zones that are designed to provide relatively lower targeted vertical deceleration levels comprise a plurality of cells that have relatively higher angles of drafting.
In one approach, a method of designing shoe midsoles comprises: selecting the application for which the shoes will be worn; determining the vertical stability requirements of the application; generating pressure distribution maps for each activity associated with the application; delineating zones on the midsole based on the vertical stability requirements and the pressure distribution maps; determining the targeted vertical deceleration level of each zone based on the vertical stability requirements and the pressure distribution maps; and selecting and varying the geometric and material properties of each zone to the extent necessary through an iterative process to achieve the targeted vertical deceleration level in each zone.
In one approach, the iterative process comprises: measuring the actual vertical deceleration level; comparing the actual and targeted vertical deceleration levels; adjusting the geometric and/or material properties within each zone as needed based on the difference between the actual and targeted vertical deceleration levels; and repeating the process until the actual and targeted vertical deceleration levels are the same.